Image sensors and methods with pipelined readout

Abstract

A pipelined readout method in an image sensor includes receiving one or more signals from a pixel of a row of a pixel array into a column storage at least partially during a time that a previously sampled amplified output of the column storage that is based on signals provided by a previous pixel of a previously read out row of the pixel array is converted from analog to digital by an analog-to-digital conversion circuit. The method further includes performing, by the analog-to-digital conversion circuit, analog-to-digital conversion of a sampled amplified output of the column storage that is based on the one or more signals from the pixel at least partially during a time that the column storage receives at least one signal from a another pixel of a subsequently read out row of the pixel array.

What is claimed is: 
     
       1. A method, comprising:
 reading out a first signal and a second signal over a column readout line from a pixel that is located in a row of a pixel array; 
 performing, by an analog-to-digital conversion circuit, analog-to-digital conversion of a signal that is obtained using the first signal and the second signal, the analog-to-digital conversion performed at least partially during a time that one or more signals are read out over the column readout line from another pixel that is located in a different row of the pixel array than said row; 
 performing, by said analog-to-digital conversion circuit, analog-to-digital conversion of another signal that is obtained using said one or more signals; 
 amplifying, by an amplifier, a particular signal that represents a difference between the first signal and the second signal to obtain said signal; and 
 resetting said amplifier during at least part of a time when the analog-to-digital conversion of said signal is being performed. 
 
     
     
       2. A pipelined readout method in an image sensor, the method comprising:
 receiving one or more signals from a pixel of a row of a pixel array into a column storage at least partially during a time that a previously sampled amplified output of the column storage that is based on signals provided by a previous pixel of a previously read out row of the pixel array is converted from analog to digital by an analog-to-digital conversion circuit; and 
 performing, by the analog-to-digital conversion circuit, analog-to-digital conversion of a sampled amplified output of the column storage that is based on the one or more signals from the pixel at least partially during a time that the column storage receives at least one signal from another pixel of a subsequently read out row of the pixel array; 
 wherein amplification for the previously sampled amplified output of the column storage is provided by an amplifier that is connected between the column storage and the analog-to-digital conversion circuit; and 
 wherein the method further includes resetting the amplifier at least partially during a time that the analog-to-digital conversion circuit performs the analog-to-digital conversion of the sampled amplified output of the column storage. 
 
     
     
       3. A method, comprising:
 reading a first signal from a pixel of a first row of a pixel array into a column storage while resetting an amplifier and autozeroing a column analog-to-digital conversion circuit; 
 reading a second signal from the pixel of the first row into the column storage; 
 amplifying an output of the column storage that represents a difference between the first signal and the second signal using the amplifier to provide an amplified difference signal; 
 sampling the amplified difference signal with the column analog-to-digital conversion circuit; 
 performing analog-to-digital conversion of the sampled amplified difference signal using the column analog-to-digital conversion circuit at least partially during a time when a signal from a pixel of a second row of the pixel array is read into the column storage. 
 
     
     
       4. The method of  claim 3 , further comprising:
 resetting the amplifier during a time when the column analog-to-digital conversion circuit performs the analog-to-digital conversion of the sampled amplified difference signal. 
 
     
     
       5. The method of  claim 3 ,
 wherein a total time period for the reading of the first signal and the second signal from the pixel of the first row into the column storage is equal to one row time period; and 
 wherein the analog-to-digital conversion of the sampled amplified difference signal lasts for longer than one-half of the row time period. 
 
     
     
       6. The method of  claim 3 ,
 wherein signals from pixels in the pixel array are read out row by row during one frame; and 
 wherein the autozeroing of the column analog-to-digital conversion circuit is performed only once per frame. 
 
     
     
       7. The method of  claim 3 , further comprising:
 amplifying, using the amplifier, a second output of the column storage that represents a difference between signals read from the pixel of the second row of the pixel array to provide a second amplified difference signal; 
 sampling the second amplified difference signal with the column analog-to-digital conversion circuit; and 
 performing analog-to-digital conversion of the sampled second amplified difference signal using the column analog-to-digital conversion circuit at least partially during a time when another signal from a pixel of a third row of the pixel array is read into the column storage.